1. Field of the Invention
The present invention relateds to pipe joints for use in piping for heat exchangers, tanks, pressure containers, etc.
2. Description of the Prior Art
With reference to FIGS. 58 to 60, a pipe 170 has at an end thereof a housing 171 which is formed with a pair of upper and lower approximately square apertures 172 in each of its opposite sides. Another pipe 173 to be joined to the housing 171 has a tapered portion 174. Provided inside the housing 171 are a bush 175 shaped in conformity with the contour of the pipe 173 and an O ring 176 positioned at the base end of the bush 175. When the pipe 173 is to be inserted into the housing 171, each of opposite legs 177a of a U-shaped stopper 177 is inserted the pair of apertures 172 of the housing. The pipe 173 is then inserted inside the housing 171 until the tapered portion 174 moves past the stopper 177. This brings a stepped part 174a of the tapered portion 174 of the pipe 173 into contact with the inner end face 177b of the stopper 177, whereby the pipe 173 is joined to the housing (see Unexamined Japanese Patent Publication No. 225290/1983).
FIG. 61 shows another pipe joint which is prepared by inserting a pipe 181 into a housing 180 and inserting a U-shaped stopper 182 into the housing 180 from outside for opposite legs 183 of the stopper 182 to hold the pipe 181 therebetween (see Examined Japanese Patent Publication No. 44876/1982).
With the former joint of the prior art, the legs 177a of the U-shaped stopper 177 need to be manually inserted into the respective pairs of upper and lower apertures of the housing 171, and a similar problem is encountered in removing the pipe 173 from the housing 171. Furthermore, the bush 175 and the O ring 176 must be set in position inside the housing 171 in advance in addition to the manual insertion of the U-shaped stopper 177. Accordingly, the pipe joint has the problem of necessitating time for joining the pipes and being inefficient to fabricate, for example, when it is used for preparing piping for an air conditioner within the limited space of engine room of the motor vehicle shown in FIG. 57. The construction wherein the U-shaped stopper 177 is inserted in the housing 171 has other problems. As shown in FIG. 60, the stopper 177 is in contact with the housing 171 locally at four portions against an external force acting in a direction to slip off the pipe 173, and concentration of force occurs at these portions. The construction is therefore undesirable from the viewpoint of strength. These portions readily permit ingress of extraneous matter, which could lead to corrosion.
With the latter pipe joint, the pipe 181 must be inserted into the housing 180 before the insertion of the stopper 182. Like the fomer, the pipe joint has the problem of a reduced work efficiency when used in the piping for automotive air conditioners.
Heat exchangers have a header pipe for distributing the heat exchange medium to the core portion. For connecting an outlet or inlet pipe for the medium to the header pipe, a union joint is used, or a pipe flange is provided at the joint end portion of each of the header pipe and the other pipe. However, these joint means have problems. The union joint requires a length of time for tightening up the union nut, while the latter necessitates labor for fastening the pipe flanges with screws.
FIG. 62 illustrates another example of joint, i.e., a joint for connecting liquid transport pipes 196 to a receiver 191. The receiver 191 has at opposite sides of its head 192 a liquid inlet portion 193 and a liquid outlet portion 194 each formed with a tubular male screw. The transport pipe 196 has an annular projection 195 close to the outer end thereof, and a cap nut 197 fitted therearound and positioned closer to the other end thereof than the projection 195. The pipe 196 is joined to each of the inlet portion 193 and the outlet portion 194 by inserting the pipe 196 into the portion and screwing the cap nut 197 on the tubular male screw.
FIG. 63 shows a receiver 201 which has a refrigerant inlet pipe 202 and a refrigerant outlet pipe 203 connected to the top of the receiver by block joints 204, 205, respectively (Unexamined Japanese Patent Publication No. 195256/1986). In this case, the block joints 204, 205 respectively have bolts 205, 207 which are screwed into holes 208 in the top portion of the receiver 201 from above with a tool, whereby the inlet and outlet pipes 202, 203 are attached to the receiver.
The former of the receivers described has an increased number of components, while the pipe must be joined to each side of the head 192 by manually turning the cap nut 192 and finally tightening up the cap nut with a tool. The joint therefore has the problem that the pipe requires cumbersome work for attachment and removal. With the latter receiver, the pipe can be attached more easily than when the cap nut is used, but the tool is indispensable for screwing or removing the bolts 206, 207, hence a low work efficiency.
FIGS. 64 and 65 show a pipe joint which comprises a first pipe 222 having an annular outer peripheral projection 221 close to a pipe end and an O ring 223 provided around a spigot portion 22a closer to the pipe end than the projection 221, and a second pipe 224 having an enlargded tubular portion 22a closer a pipe end. The enlarged tubular portion 224a of the second pipe 224 is formed with two pairs of vertically opposed small holes 224b. When the first pipe 222 is inserted into the tubular portion 224a with a U-shaped pin 225 inserted through the small holes 224b, the annular projection 221 of the first pipe 222 forces the pin 225 open to fit into the portion 224a inwardly of the pin, with the result that the first pipe 222 is joined to the second pipe 224 inside thereof.
FIGS. 66 and 67 show another pipe joint. When a first pipe 222 is inserted into an enlarged tubular portion 224a of a second pipe 224 with a ringlike stopper 227 fitted in slits 226 formed in opposite sides of the tubular portion 224a, an annular peripheral projection 221 of the first pipe 222 forces the stopper 227 open to further fit into the tubular portion inwardly of the stopper, whereby the first pipe 222 is joined to the second pipe 224.
With the former of the conventional pipe joints described, the U-shaped pin 225 is merely inserted and is therefore likely to slip off due to vibration, for example, when the joint is used for the piping for an automotive air conditioner. With the latter pipe joint, a space S is formed between the ringlike stopper 227 and the annular projection 221 of the first pipe 222, so that the first pipe 222 is liable to move at its base end side relative to the second pipe 224, for example, owing to vibration. Thus, the pipe joint has the problem of being unstable.